In semiconductor manufacturing field, planarizing a wafer is one of the important processes for fabricating a semiconductor device. In conventional art, chemical mechanical polishing (CMP) is a kind of process used for planarizing a surface of a semiconductor wafer, which combines the effects of mechanical force with the chemical reaction generated between the wafer surface and the polishing slurry. Another kind of process for planarizing a wafer surface is fixed abrasive polishing. For instance, U.S. Patent Publication NO. 20010044271 discloses a polishing pad which is formed by fixing an abrasive layer having a plurality of abrasive particles to a rigid layer. The polishing pad is mounted on a polishing platen, which includes a surface in contact with a surface of a wafer.
However, in the conventional CMP process, the polishing slurry distributes randomly on the polishing pad, which induces lots of negative problems such as an uneven density, a poor polishing result, a low utilization ratio of the slurry, and environmental pollution caused by wasted polishing slurry. Therefore, the CMP process tends to be replaced with the fixed abrasive polishing process which has advantages such as a high utilization ratio of the abrasives and an excellent polishing precision, and becomes more widely used in semiconductor manufacturing process.
FIGS. 1a and 1b are schematic cross-sectional views illustrating operating states of a fixed abrasive polishing system according to the prior art. Referring to FIG. 1a, a fixed abrasive polishing pad 102 which includes an abrasive layer is fixed on a polishing platen 101. The abrasive layer includes a plurality of abrasive blocks formed by solidifying the abrasives. A wafer 103 is fixed to a polishing head 104, and a surface of the wafer is in contact with the abrasive layer on the polishing pad 102. In operation, the fixed abrasive polishing pad 102 is driven to rotate by the rotation of the polishing platen 101. And the wafer 103 is driven to rotate by the rotation of the polishing head 104 and moves relative to the fixed abrasive polishing pad 102, which makes the surface of the wafer 103 rub against the abrasive layer to be polished. Referring to FIG. 1b, because the abrasive layer 110 formed on the fixed abrasive polishing pad 102 includes solid particles such as silica and ceria, a large number of solid particles such as silica particles 201 and ceria particles 202, are then generated by the mechanical force when the abrasive layer 110 is rubbed against the surface of the wafer 103. The solid particles have an unintended impact on the polishing performance, causing the surface of the wafer 103 scratched. As a result, the wafer is damaged and scraped. Deionized water is commonly used to rinse and wash the surface of the fixed abrasive polishing pad 102 after the wafer is polished, so as to remove the solid particles generated during the polishing process, thereby reducing the risk of scratch damage to a next wafer. However, the conventional process can not absolutely prevent damages to the wafer caused by the solid particles generated during the polishing process.